Help with vet bills

Rescued a dog last year after hearing that she has been bread and left in abandoned house she was in a terrible condition. She is a loved member of the family after rescuing her she had a pea sized lump on stomach. We had taken her to the PDSA as we are benefits they had informed us that it wasn’t anything to worry about and nothing they could do. This has now grown at a rapid pace we have now been taking out pet insurance. Taken her to the vets unfortunately insurance wasn’t valid because it was a previous illness. This pea size lump has now grown into a fist size lump and still growing at a rapid pace. We have tried throughout all of the charity for help which hasn’t been successful. We are now at a stage of not knowing was to do apart from trying to raise money to fund the vet bill that has been stated at £2000. She has had a traumatic life which we just want her to get her back to good health. Any help would be much appreciated and go a very long way. Please help our dog we don’t know what else to do but we just want to get her back right as she is now unrepeatable in the family. This need sorting as soon as possible as its getting worse.